1. Field of the Invention
This invention relates to the manufacture of a wax pattern of a bladed rotor and in particular a radial flow bladed rotor suitable for a fluid flow machine such as a gas turbine engine.
2. Description of the Related Art
Bladed rotors of the radial flow type, that is centrifugal flow compressors and radial flow turbines, typically consist of a central body rotatable about a given axis which has a number of aerofoil blades integral therewith. In the case of the centrifugal flow compressor, the blades define passages which converge in the direction of fluid flow as the flow direction changes from axial flow to radial flow. Similarly with the radial flow turbine, the blades define passages which diverge in the direction of fluid flow as the flow direction changes from radial flow to axial flow.
Since such bladed rotors are typically of integral construction it is common to manufacture them by casting using the well known "lost-wax" casting technique. In that technique, a wax pattern in the shape of the bladed rotor to be manufactured is covered with a heat resistant and hardenable material. The wax pattern is then removed by melting to leave a mould for use in the final casting operation.
The original wax patterns are frequency manufactured by injection moulding using a metal die of appropriate configuration. Such dies are expensive to manufacture and thereby make a significant contribution to the total cost of bladed rotor manufacture.